U.S. Pat. No. 4,256,759 discloses 1-methyl-beta-oxo-alpha-phenylcarbamoyl-2-pyrrolepropionitrile of formula I, ##STR2##
The compound of formula I is acidic and may exist in a tautomeric enolic form represented by formula Ia ##STR3##
Salts mentioned in U.S. Pat. No. 4,256,759 for the class of compounds are salts with pharmaceutically acceptable bases, such as alkali metal, alkaline earth metal, copper or zinc hydroxides; ammonia, mono-, di- or tri-lower (alkyl or hydroxyalkyl)-amines, alkyleneimines or alkylenediamines, e.g. sodium, potassium, magnesium, ammonium, mono-, di- or tri-(methyl, ethyl or hydroxy-ethyl)-ammonium, pyrrolidinium, ethylenediammonium or morpholinium salts; or various hydrates thereof.
Salts specifically disclosed for the compound of formula I are the sodium salt, potassium salt, calcium salt and tris-hydroxyethyl-ammonium (triethanolamine) salt. The sodium, potassium and calcium salts are not crystalline.
Tromethamine is the primary amine tris-(hydroxy-methyl)-aminomethane, also named 2-amino-2-(hydroxy-methyl)-1,3-propanediol, and described in Merck Index, Tenth Edition page 1395.
The tertiary amine triethanolamine has been converted chemically in the laboratory to N-nitrosodiethanolamine which has been implicated as a potential carcinogen. Some concerns have been expressed about triethanolamine salts as pharmaceuticals based on the speculation that triethanolamine might somehow be converted metabolically in mammals to N-nitrosodiethanolamine.
On the other hand, the primary amine tromethamine is not known to be chemically convertible to any N-nitroso derivative.